1. Field of the Invention
The present invention relates generally to an electrode for an electron gun, a method of manufacturing an electrode for an electron gun, and an electron gun assembly. In particular, this invention relates to an electrode for an electron gun, which is applicable as a first grid electrode of an electron gun assembly, a method of manufacturing the electrode for the electron gun, and an electron gun assembly including the electrode for the electron gun.
2. Description of the Related Art
In the prior art, as described in Jpn. Pat. Appln. KOKAI Publication No. 64-43952, for instance, an electron gun assembly applied to a cathode-ray tube is configured to include a cathode that emits electrons, and a plurality of electron gun electrodes disposed coaxial with the cathode.
In this type of electron gun assembly, while it is being operated, barium oxide (BaO), which is an electron emission substance of the cathode, is reduced with the emission of electrons. As a result, barium (Ba) is evaporated from the cathode. Most of the evaporated barium (Ba) tends to easily deposit on a first grid electrode, which is one of a plurality of electron gun electrodes and is disposed near the cathode.
In an electron gun assembly described in Jpn. Pat. Appln. KOKAI Publication No. 64-43952, it is intended to positively remove the deposited barium (Ba) by a reduction action of a metal coat film formed on a surface of the first grid electrode. However, the metal coat film is easily oxidized in the manufacturing process of the cathode-ray tube and thus the metal coat film cannot fully function. Consequently, a barium film may easily deposit on the surface of the first grid electrode.
If a barium (Ba) film deposits on the surface of the first grid electrode with the passing of operation time, as mentioned above, the barium film may possibly remove and drop from the first grid electrode due to various factors such as vibration. The removed barium film may short-circuit the first grid electrode and the cathode, or the first grid electrode and the second grid electrode. Hence, the performance of the electron gun assembly may deteriorate, or a fault may occur in the electron gun assembly, which leads to degradation in reliability.